Laser materials processing as known in the art and as used herein refers to performance of materials processes such as cutting, welding, drilling and soldering, using a high power continuous wave or pulsed laser beam. The average power of a high power laser beam may range from as little as approximately one watt to hundreds of watts. A user selects the specific power of the beam on the basis of the particular process being performed.
Known art desribes transmitting a laser beam from a laser source to the vicinity of a workpiece by means of an optical fiber. For example, an apparatus and method for injecting a power laser beam into an optical fiber for transmission therethrough are described in commonly assigned U.S. Pat. Nos. 4,564,736, 4,676,586, and 4,681,396 respectively entitled "Industrial Hand Held Laser Tool and Laser System", "Apparatus and Method for Performing Laser Material Processing Through a Fiber Optic", and "High Power Laser Energy Delivery System", the disclosure of each of these patents being incorporated in their entirety herein by reference.
Transmitting a laser beam through an optical fiber to an output coupler also is known. Such an apparatus is described in commonly assigned U.S. Pat. No. 4,799,755, entitled "Laser Materials Processing with a Lensless Fiber Optic Output Coupler", the disclosure of which is incorporated in its entirety herein by reference. In the apparatus described in U.S. Pat. No. 4,799,755, lens systems are not utilized in an output coupler. Rather, a fiber injecting lens is selected to have a focal length of sufficient length to enable the use, for materials processing, of the diverging beam emitted at an output end of the fiber without a need for a beam focusing lens-type output coupler.
An output coupler having a lens system therein for focusing a laser beam transmitted thereto through an optical fiber is disclosed in commonly assigned U.S. Pat. No. 4,844,574, entitled "Optical Fiber Output Coupler for a Power Laser", the disclosure of which is incorporated in its entirety herein by reference. The apparatus described in U.S. Pat. No. 4,844,574 includes a lens system that compensates for adverse effects of fiber transmission in order to improve focused spot power density of the fiber transmitted beam. The lens system illustrated in U.S. Pat. No. 4,844,574 causes a beam to undergo focusing action within the output coupler. In high power laser beam transmission, however, focusing a beam within the coupler is undesirable because the focused beam may cause air in the coupler to ionize. The ionized air will deflect the high power laser beam passing through the coupler and the beam may impinge against and damage components within the coupler. At col. 12, lines 9-16 in U.S. Pat. No. 4,844,574, it is pointed out that a plano-concave or double concave lens which would provide a diverging beam could be utilized, thereby eliminating problems related to focusing a beam within the coupler.
Still other known laser material processing systems utilize lens systems at an output of a laser source. Such systems are described in U.S. Pat. Nos. 3,419,321 and 4,275,288, entitled "Laser Optical Apparatus for Cutting Holes" and "Apparatus for Machining Material", respectively. In each of these systems, optical fibers are not utilized. Therefore, since a laser source generally is a stationary system, at least during a materials processing operation, lenses are aligned with the beam directly output by the laser source. The mobility of such systems is limited.
Further, in some of the above-described systems, in order to perform a materials processing operation on a portion of a workpiece surface larger than the focused spot, either the workpiece or the output coupler must be moved, such as by robotic arm, in order to complete the operation. For example, in a drilling operation, in order to form a large diameter opening such as greater than 40 mils, the output beam of the coupler is focused on the workpiece, and a robotic arm moves the coupler and/or the workpiece, in accordance with a pre-programmed path, along the circumference of the opening being formed. That is, a system operator predetermines a path of movement for the coupler and/or workpiece and, through a user interface to a robotic unit, enters instructions to the robotic unit to control movement of its robotic arm. The workpiece and/or coupler are then engaged to the robotic arm, and during the drilling operation, the output coupler is moved relative to the workpiece, or the workpiece is moved relative to the coupler, to complete the operation.
Programming a robotic unit is a time-consuming task, and the successfulness of the operation depends on the expertise and experience of the system operator. Further, once the material processing operation begins, if the operator determines, for example, that a different diameter hole should be drilled, changes to the pre-programmed operation are necessary. The drilling operation must be stopped and the robotic unit re-programmed. That is, on-the-fly changes to the size, i.e. diameter, of a hole being drilled are not possible. Rather, with known systems, the entire operation is stopped in order to reprogram the robotic unit therefore increasing the time required to complete the operation.
Moreover, in operation, robotic units vibrate, and this vibration generally is transmitted to the arm of the robotic unit. Therefore, it is very difficult to precisely drill a specific diameter opening. Further, when it is desired to form an irregular shaped opening or even an ellipse-shaped opening, controlling the motions of the robotic arm to precisely form the desired opening is even more difficult. In some operations where precision is necessary, therefore, known systems cannot be used.
It is therefore an object of the present invention to provide a materials processing system which utilizes an optical fiber for transmitting a high power beam to an output coupler, the output coupler having beam shaping optics for controlling the shape of a laser beam output from the coupler.
Another object of the present invention is to provide a materials processing system including an optical fiber and an output coupler which allows on-the-fly variability to a materials processing operation such as varying the diameter of an opening being drilled.
Still another object of the present invention is to provide a materials processing system without requiring that the workpiece or the output coupler undergo trepanning motions to complete a materials processing operation, such as drilling various diameter holes.
Still yet another object of the present invention is to provide a materials processing system including an optical fiber and an output coupler which allows more precise execution of materials processing operations including forming irregular shaped openings to specific dimensions.